This is what the browser displays if I turn SSL off in plesk and try to use port 443 in Litespeed:
Apache/2.0.51 (Fedora) mod_perl/1.99_12 Perl/v5.8.3 DAV/2 mod_auth_pgsql/2.0.1 PHP/4.3.10 mod_python/3.1.3 Python/2.3.3 mod_ssl/2.0.51 OpenSSL/0.9.7a FrontPage/5.0.2.2635 Server at www.uslister.com Port 443

Ok one of the the reasons I am trying to do this is I have a dedicated server running php4 on plesk but had a billing module that the developer made for php5 by mistake. I will eventually be moving entire server of 35 websites over to a new server but in the mean time I would like php5 to run on one domain in plesk. I manually added listener and virtual host for just the one site for now until I can fully test lightspeed with php5 as alot of sites can break with the switch as well as some minor issues with litespeed and plesk. Litespeed is set up on port 2443 right now and I already compiled php 5.24 and it is working. Just want to try to make the url transparent like https://www.example.com instead of https://www.example.com:2443. I also want to one by one start testing the websites and ironing out any php5 incompatibilities and litespeed problems. Is there a way to move sites in php4/plesk/apache to php5/plesk/litespeed one at a time so I can have a smooth transtion and 0 downtime? If it wasn't for the amount of sites I wouldn't worry. I tried disabling ssl for the domain that litespeed is being used for but the default port 443 still can't be used as apache still owns it apparently? What are your thoughts?

The PHP support in LiteSpeed is the best, you can use php4 for one part of the site, while using php5 for another part of the site, setup is easy, there are a few threads about this on the forum already.

I would recommend converting all sites from Apache to LiteSpeed all at once, instead of one by one. you can verify all site on a different port like 2080 and 2443. If nothing obviously broke, then turn off Apache and let LiteSpeed take port 80 and 443.

Minor issues can be addressed later. should be very few if any. just let us know if need help.